Explosive device

ABSTRACT

The invention is concerned with an explosive device for seismological marine reconnaissance, the device comprising a tubular casing containing the explosive charge and a detonator in which the detonator is provided with a plastics closure plug the plug being extended so that it projects beyond the end of the detonator and engages in the bottom opening in the casing containing the charge so as to seal the same against the ingress of seawater. To increase the sealing action the bottom end of the casing may comprise a conical portion terminating in a cylindrical neck, the extended end of the aforesaid plug having a flange for co-operation with the said conical end of the casing.

C United States Patent [151 3,675,574 Moreau [4 1 July 11, 1972 [s41 EXPLOSIVE DEVICE 3.49|,es7 umo Cholet .102/24R [72] lnvemcr: 2 Jules Hem Yonne' Primary Examiner-Verlin R. Pendegrass rance Al!0rne \'JamcS & Franklin [73] Assignee: Societe: Etabllsements Davey Blcldord Smith 8: Cie Societe Anonyme Francaise. [57] ABSTRACT Saint Maur Rouen, France The invention is concerned with an exploslve device for Flkdl 0% seismological marine reconnaissance, the device comprising a [30] Foreign Application Priority Data Nov. 28. i969 France ..694l252 [52] U.S.Cl 4 ...tl02/24, l02/28 [51] Int. Cl t ..F42b 3/12 [58] Field of Search 102/24, 28; 18l/.5 KC

[56] Relerences Cited UNITED STATES PATENTS 3.360.070 l2/l965 Cholet et al ..lO2/24 R Appl. No.: 83,840

tubular casing containing the explosive charge and a detonator in which the detonator is provided with a plastics closure plug the plug being extended so that it projects beyond the end of the detonator and engages in the bottom opening in the casing containing the charge so as to seal the same against the ingress of seawater. To increase the sealing action the bottom end of the casing may comprise a conical portion terminating in a cylindrical neck, the extended end of the aforesaid plug having a flange for co-operation with the said conical end of the casing.

ll Claims, 5 Drawing figures PATENTEDJuL 1 1 I972 FIG.3

Aunts 11/1. 4:: have: Moi! EXPLOSIVE nsvrcs The present invention relates to a safety explosive device for seismological marine prospecting.

The increasingly intensive working of olfshore petroleum and gas deposits have given rise to considerable development of the so-called seismic marine" technique, the object of which is the study of submarine geology.

in one of its most common forms this technique utilizes explosive charges which are fired below water at regular intervals over a selected path or area so that the explosion points are suitably distributed over the zone to be studied. The large number of firings required and consequently the rhythm of firing have led to the development of extensively automated systems for the operation of which the explosive may usefully be made available in a special pack or cartridge. In addition, the electric detonators required for firing the cartridges also entail special presentation suitable for the method of supply of the electric current which is characteristic of the firing processes in question.

Thus the process commonly known as Flexotir" utilizes cartridges contained in special casings. The latter are launched, i.e. submerged by feeding them into a flexible loading tube, one end of which is fixed to the stam of the ship, while the other end trails in the sea at a certain depth. The casing driven by a flow of water, becomes blocked in fluid-tight manner at the bottom end of said tube. At this moment the two conductors supplying current to the detonator wires are provided on the one hand by the mass of the sea in contact with one of the wires and on the other hand the column of seawater contained in the tube and in contact with the other wire. It is therefore necessary for the detonator to be capable of completing the electric circuit and for the cartridge itself to be suitable for this special detonator.

The first essential therefore is that one of the two conductors of the primer head should be in contact with the seawater outside the case and, secondly, that a stopper of suitable shape should form a break in continuity between the sea and the column of seawater within the case and the flexible tube connecting with the ship. Finally, it is necessary for the other conductor of the primer head to be in contact with this column of seawater. In order to ignite the detonator it is then sufficient to supply a suitable current to the circuit comprising the sea, the primer head and the column of water contained in the tube and the case.

in addition, in order to comply with regulations and safety requires, the cartridges must not be held "in store once they have been primed by fitting the detonators.

Finally, from the point of view of economy it is necessary to be able to prime and load the cartridges at a rapid rate, so that no complicated manipulations or operations are involved.

The applicants have conceived an explosive device which solves the problem posed and also complies with the conditions indicated above and which by utilizing a detonator of special design is equally suitable for plastic explosives and for pulverulent explosives, while taking into account the conditions of utilization determined by the constitution of the case.

The present invention consists in extending the closure plug of the detonator, which plug is of plastics or other non-conductive material, so that its projecting end functions as a plug to close the orifice or a neck formed in the lower end of the casing containing the explosive charge so as to provide a fluidtight closure therewith, which orifice or neck is of reduced cross section, the detonator plug having a primer wire which extends at both ends thereof to establish the necessary electrical circuit at one end with the sea water and at its other and inner end with the case of the detonator and thus with the water in the loading tube.

According to a preferred embodiment of the present invention the explosive device comprises the combination of a cas ing adapted to contain an explosive cartridge and provided at its base with a conical portion extended by a cylindrical neck constituting the bottom orifice of the case, and a detonator of conventional type but which includes a plastics closure plug which is extended to form, outside the metal case of the detonator, on the one hand a circular lip capable of bearing against the wall of the conical portion of the base of the casing and on the other hand to function as a second plug inserted into the neck of said casing in order to form a fluidtight closure for the casing, one of the primer wires extending through said plug so that its outer end makes contact with the sea water, while the second primer wire is in contact with the metal case of the detonator in order to be connected to the column of seawater container in the case and in the flexible submersible loading tube by means depending on the type of cartridge used, the detonator plug effecting in all cases a break in continuity between the sea and said column of water. Whether the explosive contained in the cartridge is of the plastic or pulverulent type, the electrical connection means between the detonator case and the column of water contained in the casing may be constituted by a blind tubular detonator carrier electrode of plastics material which receives the detonator, and of which the portion constituting its bottom is traversed by a conductor wire of sufficient length to pass through the cartridge and form at one end an antenna above the cartridge in said column of water and, at its end, to make contact with the case of the detonator.

In one arrangement the tubular primer holder may be provided at its base with a collar limiting the depth to which it can project into the explosive cartridge.

In another arrangement, the tubular primer holder may be provided at its base with an annular cup of a size to enclose the bottom portion of the explosive cartridge.

in the case of a pulverulent explosive cartridge the electrical connection means between the detonator case and the column of water contained in the casing of the device may, as an alternative, be constituted by a cylindrical tube of conductive metal enclosing the explosive and provided at its base with a re-entrant recess which serves as detonator carrier electrode and within which the detonator is a friction fit in order to make electrical contact between the tube and the detonator case, a plug, for example made of plastics material, closing the tube at its top portion, while the tube makes the electrical connection between the detonator and the column of water into which the cartridge is inserted.

One embodiment of the invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a part sectional elevation of the explosive device;

FIG. 2 is a section on an enlarged scale showing the detonator;

FIG. 3 is a section of a primed explosive cartridge equipped with a detonator carrier electrode of plastics material;

FIG. 4 is a section of a cup type detonator carrier electrode of plastics material, and

FIG. 5 is a section of a primed pulverulent explosive can tridge with metallic casing.

Referring to FIG. 1, the device comprises a rigid casing l, e.g. of plastics material, having a cylindrical or slightly conical body extending between a conical collar 2, intended to be blocked, (i.e. of a size to fill the interior cross section of the tube), in the end of the flexible submersible tube and an end or bottom portion 3 of sharply conical shape terminating in a cylindrical neck 4 of small diameter which is open at the bottom, the interior of the uncharged casing thus being in direct communication with the sea. 7 indicates a cartridge containing the explosive charge which, as explained below, is placed in the casing.

When charging is effected, the base end of a special detonator 5 (see FIG. 2) contained by a detonator carrier electrode 6 introduced into the explosive cartridge 7 is engaged in the conical terminal portion 3. The detonator 5 is of conventional type with regard to its electrical and pyrotechnical structure. it comprises a deep-drawn case of conductive material, e.g. copper or aluminum, having a crimped lower end into which there is inserted a primer head represented in the drawing by its filament 8. A plug 9, which is normally of small dimensions and projects only slightly from the detonator case,

assumes much greater importance in this particular construction. It is in fact developed to form a sealing means, not only for the detonator but also for the bottom inlet to casing I, being engaged in the cylindrical neck 4 and bearing on the conical bottom 3 of the said casing, assisted to that end by the thrust of the incoming water and the static pressure set up by the same. thus providing a break in continuity required between the column of water formed in the submersible tube and the sea.

The plug 9 modified for this purpose comprises an annular li 9a which, as shown in FIG. I, bears against the conical bottom 3 and can by itself alone constitute the sealing means for the closure of the casing. It is, however, preferably to terminate the plug by a cylindrical or, preferably, as shown, a taper portion 9b extending beyond said lip and engaging, as has been stated, in the neck 4 of the casing. In addition to a shape adapted to sealing requirements, it is of course necessary to give this plug the desirable mechanical characteristics, particularly flexibility.

As the case of the detonator 5 is conductive, the end 80 of primer head 8 is placed on contact with it radially through the plug 9 in the direction of the crimping 8a.

The other end of the primer head is connected in the usual manner to a short primer wire 10, for example 7 to 10 cm in length, which may be insulated over a length of 4 to 5 cm at the plug end, although this is not indispensable. The detonator can be mounted in two different ways in the cartridge, depending on the shape given to the latter.

FIG. 3 shows a detonator 5 introduced into a cartridge 7 containing a plastic or pulverulent (powder type) explosive. In this case the cartridge is of conventional type and cylindrical in shape, its case being made of paper, usually waxed. Its outside diameter is substantially equal to the inside diameter of the case 1 at the boundary of the bottom cone 3 of the latter. The cartridge 7 may be produced in an automatic machine of conventional type.

A detonator electrode carrier 6, composed of a blind cylindrical tube, is introduced into the cartridge 7. In the end of the tube is an antenna 11 which is in alignment with the axis of the tube and made of a metal or other conductive material which does not suffer from contact with the explosive material. The tube 6 itself may be made of any metallic or plastics material, which may be a good conductor. If this material is conductive, the antenna is fixed at this end by welding or by any mechanical fastening allowing the passage of electric current. If the tube 6 is not conductive, for example if it is made of any usual synthetic material, such as polyvinyl chloride, the antenna passes through the bottom of the case in such a manner that the detonator introduced into the tube is in electrical contact with it, as shown in FIG. 3.

In order to improve the electrical circuit, it is also possible to coat the interior of the detonator carrier electrode with a conductive varnish.

The open end of the detonator electrode carrier may be formed with a flange 60, as shown in FIG. 3, in order to limit the penetration of the detonator carrier into the cartridge, or else it may be formed with a circular cup 6b, as shown in FIG. 4, in order to receive the bottom end of the cartridge. Slight ovalization of the tube 6 or the provision of ribs in relief on one or more generatrices may assist in holding the detonator in position in a recess formed for the purpose in the cartridge.

The dimensions of the primer carrier tube 6 are such that the detonator 5, when fully engaged in the tube, protrudes sufficiently from the latter to enable its plug 9 to be engaged against the conical bottom of the casing l in order to establish the seal, while the cartridge itself is placed in the bottom end of the cylindrical (or conical end portion) of the casing 1.

In order to place the detonator electrode carrier 6 in position in the cartridge, it is passed axially through the open end 4 of the latter, first inserting the antenna I 1 which projects a few centimeters at the other end of the cartridge until the collar 6a or cup 6b of the carrier bears against its first end. In this application to cartridges containing plastics or pulverulent explosive, the first portion of the circuit is formed by bringing the case of the detonator S into contact with the bottom end of the antenna 11, which itselfis in contact with the column of water formed in the flexible submersible tube.

The second portion of the circuit is formed by the axially extending end of wire [0 through the plug 9 and through the cylindrical orifice 4 in the bottom end of the case I, the wire then being in open contact with the sea water.

When the detonator is applied to a cartridge 12 containing pulverulent explosive, as shown in FIG. 5, having a metal collar or in a metal case, it may be introduced directly into the cartridge without using an electrode carrier. The cartridge l2 in FIG. 5 has the form of a blind cylindrical tube, the outside diameter of which is substantially equal to the inside diameter of the casing l at the boundary of the bottom cone. Its upper end is open in order to enable it to be filled in an automatic cartridge making machine of conventional type. After being filled, this tube is closed by a cap or plug 13. Its bottom end which is closed is provided with a re-entrant recess 12a in order to act as a carrier for the detonator electrode. This recess is dimensioned on the same basis as the tube 6 of the detonator carrier described previously, and the detonator 5 is held in frictional engagement therein in the same manner, its free conductor being directed downwards. Such friction may be obtained by ovalization of the section of the recess or by the formation of reliefs along one or more directions, or by any other means.

Since tube 12 is made of a conductive material and is not damaged by contact with the explosive material and since contact is made between the deep-drawn body of the detonator 5 and the recess there is consequently no break in electrical continuity between the end of the priming head connected to the mass of the body and the case which is immersed in the dolumn of sea water. The other half of the circuit is identical to that previously described.

The cartridges described above are, therefore, provided in advance with a recess for the detonator and constitute one of the two electrodes of the explosive system, namely the one which will be in contact with the column of water. Simply placing the detonator 5 in position completes the explosive system or unit by supplying it with its second electrode, namely the one which will be in contact with the seawater. Finally, when the explosive system is placed in position in the case the detonator plug provides the break in continuity required between the sea and the column of water.

The device forming the object of the invention is more particularly utilizable for petroleum deposit prospecting by the so-called seismic marine technique. As it is designed for effecting firing in an electrolyte environment, it may also be applied to a terrestrial seismic technique which would use containers filled with electrolyte.

What is claimed is:

l. A safety explosive device for seismological marine prospecting comprising a tubular casing having nose and head terminations, the casing being connected to a flexible loading tube submerged in the seawater and containing the explosive cartridge and a detonator, the improvement in which the casing is provided at its nose end with an open ended neck portion of reduced cross section and the detonator, which is of conventional type, has a closure plug of plastics material, said plug being formed with an extended portion adapted to enter into fluidtight engagement with the neck portion of the casing in order to close the same against ingress of seawater, one of the primer conductors of the detonator having an extended end which traverses the extended portion of the plug to establish electrical contact with the seawater, while a second conductor is in contact with the metal case of the detonator to establish connection with the column of water contained in the casing of the device and in the submersible loading tube, the detonator plug providing in all cases a break in continuity between the sea and said column of water.

2. A device as claimed in claim I in which the casing cornprises a cylinder formed at its lower end with a conical end portion extended by a cylindrical neck.

3. A device as claimed in claim 2 in which the closure plug for the detonator comprises an annular flange adapted to make contact with the conical end portion of the cylinder.

4. A device according to claim 3 when used with a cartridge in which the explosive is of the plastic or pulverulent type, in which the electrical connection between the case for the detonator and the column of water contained in the casing of the device is provided by a detonator carrier formed of plastics material and having a blind end portion, the blind end portion being traversed by a conductor wire of a length to extend through the cartridge and to provide at that one end an antenna above the cartridge in said column of water, and at its other end to make contact with the case of the detonator.

5. A device according to claim 3 in which the tubular carrier for the electrode of the detonator is provided at its base with an annular cup and the explosive cartridge is dimensioned at its lower end to fit within the cup and formed with a counterbore to receive the detonator carrier.

6. A device according to claim 3 when used in a cartridge containing pulverulent explosive in which the casing comprises an open top cylindrical tube of conductive material containing the explosive, and is provided at its base with a re-entrant recess to receive the carrier for the detonator electrode, said carrier being a Eriction fit within the recess in order to make electrical contact between the tube and the detonator case, the electrical connection between the detonator and the column of water in which the cartridge is immersed being provided by the tubular casing which is closed at its upper end by a plug of plastics material.

7. A device according to claim 1 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.

8. A device according to claim 2 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.

9. A device according to claim 3 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.

10. A device according to claim 4 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.

1 l. A device according to claim 5 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.

t i l 

1. A safety explosive device for seismological marine prospecting comprising a tubular casing having nose and head terminations, the casing being connected to a flexible loading tube submerged in the seawater and containing the explosive cartridge and a detonator, the improvement in which the casing is provided at its nose end with an open ended neck portion of reduced cross section and the detonator, which is of conventional type, has a closure plug of plastics material, said plug being formed with an extended portion adapted to enter into fluidtight engagement with the neck portion of the casing in order to close the same against ingress of seawater, one of the primer conductors of the detonator having an extended end which traverses the extended portion of the plug to establish electrical contact with the seawater, while a second conductor is in contact with the metal case of the detonator to establish connection with the column of water contained in the casing of the device and in the submersible loading tube, the detonator plug providing in all cases a break in continuity between the sea and said column of water.
 2. A device as claimed in claim 1 in which the casing comprises a cylinder formed at its lower end with a conical end portion extended by a cylindrical neck.
 3. A device as claimed in claim 2 in which the closure plug for the detonator comprises an annular flange adapted to make contact with the conical end portion of the cylinder.
 4. A device according to claim 3 when used with a cartridge in which the explosive is of the plastic or pulverulent type, in which the electrical connection between the case for the detonator and the column of water contained in the casing of the device is provided by a detonator carrier formed of plastics material and having a blind end portion, the blind end portion being traversed by a conductor wire of a length to extend through the cartridge and to provide at that one end an antenna above the cartridge in said column of water, and at its other end to make contact with the case of the detonator.
 5. A device according to claim 3 in which the tubular carrier for the electrode of the detonator is provided at its base with an annular cup and the explosive cartridge is dimensioned at its lower end to fit within the cup and formed with a counterbore to receive the detonator carrier.
 6. A device according to claim 3 when used in a cartridge containing pulverulent explosive in which the casing comprises an open top cylindrical tube of conductive material containing the explosive, and is provided at its base with a re-entrant recess to receive the carrier for the detonator electrode, said carrier being a friction fit within the recess in order to make electrical contact between the tube and the detonator case, the electrical connection between the detonator and the column of water in which the cartridge is immersed being provided by the tubular casing which is closed at its upper end by a plug of plastics material.
 7. A device according to claim 1 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.
 8. A device according to claim 2 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.
 9. A device according to claim 3 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.
 10. A device according to claim 4 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge.
 11. A device according to claim 5 in which the tubular carrier for the detonator electrode is provided with a collar by which it is located within the explosive cartridge. 